1. Field of Invention
This invention relates generally to innersoles for sneakers and other athletic shoes, and more particularly to an innersole that is adjustable to impart thereto characteristics appropriate to the particular use for which the shoe is to be put.
2. Status of Prior Art
In a shoe, the insole is the innersole of the shoe overlying the outer sole. When the insole is an extra strip of material that is put inside the shoe for comfort or protection, it is then referred to as an innersole. In an athletic shoe such as a sneaker, the requirements of an innersole depend on the particular use to which the sneaker is to be put.
A wearer of sneakers engages in various forms of sports activity, such as playing tennis or basketball, jogging, jumping, long distance running as well as racing at high speed for a short distance. In these activities, the ground may in some cases be paved and hard, while in other cases it may be formed of dirt, grass or clay.
Hence an innersole whose characteristics are suitable for one type activity may be inappropriate for other types. For example, when running in a marathon on paved city streets for twenty miles or more, then the sneakers best suited for this purpose should have shock absorbing characteristics, for otherwise the runner will experience foot pain as he continues to pound hard paved surfaces.
But if the same runner is in a race over a short distance on a dirt track, and his speed is of primary concern, then what is called for is an innersole that has spring-like characteristics which impart bounce to the sneaker to increase the runner's speed. And in many instances what is called for is an innersole whose properties are a cross or compromise between shock-absorbing and spring characteristics.
Of prior art interest is the patent to Rudy U.S. Pat. No. 5,741,568 disclosing a fibrous shock-absorbing cushion for a shoe encapsulated in a hermetically sealed envelope.
In Signore U.S. Pat. No. 4,610,099, a shoe is provided with a shock absorbing inflated air pocket. Also providing air-filled bladders in a shoe is the Johnson U.S. Pat. No. 4,446,634.
The athletic shoe disclosed in Pettibone U.S. Pat. No. 5,671,552 is designed for jumping activities, the sole of the shoe being provided with several compressible helical springs as well as an inflated air bladder. Hence this shoe combines mechanical and pneumatic actions.
The Medrano U.S. Pat. No. 4,571,853 discloses a shoe insert formed of a foam plastic pad enclosed within a plastic film envelope having holes therein whereby when the insert is compressed by the foot of the wearer, air expelled from the pad is discharged through the holes in the envelope to ventilate the foot received in the shoe.